Cloud computing is an Internet-based computing method, by which shared software and hardware resources and information may be provided for computers and other devices according to requirements. A virtualization technology, as a keystone of cloud computing, virtualizes one physical computer into multiple virtual machines (Virtual Machines, VMs), and provides, through a management system, capabilities for automatic deployment and fast provisioning of services, so that end users (tenants) may quickly and conveniently lease the virtual machines.
Because users have control rights over the virtual machines used by the users, cloud computing is also faced with some security problems while providing convenient and fast virtual machine services. For example, without permission, a user changes an Internet protocol (Internet Protocol, IP) address or a media access control (Media Access Control, MAC) address, causing a conflict and even network breakdown. Because a virtual machine accesses a network through a switch, to solve the foregoing problems, a binding relationship including an IP address and a MAC address of the virtual machine may be stored in the switch, thereby ensuring that only a legal user can access the network.
After migration of the virtual machine, the binding relationship including the IP address and MAC address of the virtual machine before the migration is still stored in the switch; as a result, the switch considers that messages sent by the virtual machine after the migration are invalid, and therefore discards the messages sent by the virtual machine after the migration, so that it is impossible to implement network access after the virtual machine migration and impossible to implement communication after the virtual machine migration.